TweetFollow Us on Twitter

September 95 - MPW Tips and Tricks: Customizing Source Control With SourceServer

MPW Tips and Tricks: Customizing Source Control With SourceServer

Tim Maroney

When two engineers on a team edit the same source file at the same time, the resulting chaos can be terrible to behold. Source control was invented to mitigate the problem. Most Macintosh programmers are familiar with the MPW Shell's Check In and Check Out dialogs, and with its Projector commands. The next frontier of custom source control involves SourceServer, a nearly faceless application that implements most of the Projector commands. MPW scripts are easy to write, but they're no match for the power, speed, and friendliness of compiled software. SourceServer exports Projector commands as Apple events, allowing source control from compiled software without launching the MPW Shell in all its pomp and splendor.

Popular third-party development environments often send Apple events to SourceServer for integrated source control. You can also use SourceServer to customize Projector beyond what you might have thought possible. For instance, you can drag source control, kicking and screaming, into the modern world of user experience with drop-on applications. In this column, I'll show you how to check a file in or out with a simple drag and drop, and how to use SourceServer for other things as well. The sample code is provided on this issue's CD; SourceServer is distributed, with documentation, on the MPW Pro and E.T.O. CDs (available from Apple Developer Catalog) and with third-party development systems.


Apple events have many faces, but they're primarily a way of communicating between different applications.

Each Apple event encapsulates a message as a command with any number of input parameters; the receiver of the message may return any number of result parameters to the sender. The most basic unit of data is the Apple event descriptor, which consists of a type code and a data handle. Apple events are built out of descriptors and are themselves special kinds of complex descriptors.

    For an excellent introduction to Apple events, see "Scripting the Finder From Your Application" by Greg Anderson in develop Issue 20.*

SourceServer's commands are represented as descriptor lists. Its Apple events are exact duplicates of the MPW Shell's Projector commands, but to avoid the overhead of a full command parser, both the command name and each argument are descriptors in the descriptor list. This saves you the trouble of putting quotes and escapes into arguments that might contain spaces or other special characters. The downside is that you have to expand arguments yourself: you can't pass in MPW wildcard characters, backquoted commands for expansion, or other special constructs.

Creating descriptor lists may sound harder than writing MPW scripts, but that's only because it is. I've provided some utility routines to ease the way, though. Listing 1 shows the utilities and illustrates how to make a command to check out a file for modification. As illustrated in the CheckOut routine in this listing, you call the CreateCommand routine first and then use the AddXArg routines to add arguments.

Listing 1. Creating SourceServer commands

OSErr CreateCommand(AEDesc *command, CString commandText)
// Begin a new SourceServer command; name of command is in
// commandText.
   OSErr err = AECreateList(NULL, 0, false, command);
   if (err != noErr) return err;
   err = AddCStringArg(command, commandText);
   if (err != noErr) (void) AEDisposeDesc(command);
   return err;

OSErr AddCommentArg(AEDesc *command, StringPtr comment)
/* Add a "-cs comment" argument to a SourceServer command. */
   OSErr err;
   if (comment[0] == 0) return noErr;
   err = AddCStringArg(command, "-cs");
   if (err != noErr) return err;
   err = AddPStringArg(command, comment);
   return err;

/* Other SourceServer argument utilities */
OSErr AddDirArg(AEDesc *command, short vRefNum, long folderID);
OSErr AddProjectArg(AEDesc *command, StringPtr projectName);
OSErr AddUserArg(AEDesc *command, StringPtr userName);
OSErr AddFullNameArg(AEDesc *command, FSSpec *file);
OSErr AddPStringArg(AEDesc *command, StringPtr string);
OSErr AddCStringArg(AEDesc *command, CString string);

OSErr CheckOut(FSSpec *file, StringPtr userName,
               StringPtr projectName, StringPtr comment)
/* Create a "Check Out Modifiable" command for SourceServer: */
/* CheckOut -m -cs <comment> -d <dir> -project < */
/*           project> -u <user> <file> */
   OSErr             err;
   AEDesc          command;
   CStringHandle    output = NULL, diagnostic = NULL;

   err = CreateCommand(&command, "CheckOut");
   if (err != noErr) return err;
   err = AddCStringArg(&command, "-m");
   if (err == noErr) err = AddCommentArg(&command, comment);
   if (err == noErr)
     err = AddDirArg(&command, file->vRefNum, file->parID);
   if (err == noErr) err = AddProjectArg(&command, projectName);
   if (err == noErr) err = AddUserArg(&command, userName);
   if (err == noErr) err = AddPStringArg(&command, file->name);
   if (err == noErr)
     err = SourceServerCommand(&command, &output, &diagnostic);
   (void) AEDisposeDesc(&command);
   /* Display output or diagnostic text as desired. */
   if (output != NULL) DisposeHandle((Handle) output);
   if (diagnostic != NULL) DisposeHandle((Handle) diagnostic);
   return err;

Some of the utilities take Pascal strings, while others take C strings, which could well be considered bad programming practice. I chose this dubious method not because I'm on drugs, but because Pascal strings and C strings are used in different ways. SourceServer's text descriptors are C strings; when passed to these utilities as string constants, they shouldn't be converted from Pascal format in place, since some compilers put constants in read-only areas. If you're internationally savvy, you may have another objection: string constants themselves are bad practice. However, for better or worse, MPW scripts and tools are not internationalized. Just like aliens in Star Trek, all MPW programmers are assumed to speak English.

While on the subject of programming practice, I must gently reprimand SourceServer for its approach to Apple events, in which script commands are simulated through a single 'cmnd' event. SourceServer's idiosyncratic convention dates from the earliest days of Apple events, and modern guidelines discourage this type of design. An application implementing its own Apple events should designate a different command code for each operation, treating arguments as keyword parameters.

Listing 2 shows how to send an Apple event to SourceServer. It's first necessary to find and perhaps launch the SourceServer application. The snippet called SignatureToApp (by Jens Alfke) on this issue's CD accomplishes this with a single function call. Simply pass in the creator code of SourceServer, which is 'MPSP'.

Listing 2. Sending commands to SourceServer

OSErr SourceServerCommand(AEDesc *command, CStringHandle *output,
                          CStringHandle *diagnostic)
   AppleEvent            aeEvent;
   AERecord              aeReply;
   AEDesc                sourceServerAddress, paramDesc;
   ProcessSerialNumber   sourceServerProcess;
   /* SignatureToApp requires this due to a minor bug */
   FSSpec                appSpec;
   long                  theLong, theSize;
   DescType              theType;
   OSErr                 err;

   *output = *diagnostic = NULL;   /* default replies */
   /* Find the SourceServer process and make a descriptor for its */
   /* process ID. */
   err = SignatureToApp('MPSP', NULL, &sourceServerProcess,
                         &appSpec, NULL, Sig2App_LaunchApplication,
                         launchContinue + launchDontSwitch);
   if (err != noErr) return err;
   err = AECreateDesc(typeProcessSerialNumber,
                      (Ptr) &sourceServerProcess,
   if (err != noErr) return err;

   /* Create and send the SourceServer Apple event. */
   err = AECreateAppleEvent('MPSP', 'cmnd', &sourceServerAddress,
                           kAutoGenerateReturnID, kAnyTransactionID,
   /* done with the address descriptor */
   (void) AEDisposeDesc(&sourceServerAddress);
   if (err != noErr) return err;
   /* add the command */
   err = AEPutParamDesc(&aeEvent, keyDirectObject, command);
   if (err != noErr) { (void) AEDisposeDesc(&aeEvent); return err; }
   err = AESend(&aeEvent, &aeReply,
                kAEWaitReply + kAENeverInteract, kAENormalPriority,
                kNoTimeOut, NULL, NULL);
   (void) AEDisposeDesc(&aeEvent);   /* done with the Apple event */
   if (err != noErr) return err;

   /* Check for an error return in the keyErrorNumber parameter. */
   err = AEGetParamPtr(&aeReply, keyErrorNumber, typeInteger,
                      &theType, &theLong, sizeof(long),
   if (err == noErr && (err = theLong) == noErr) {
      /* Get the standard output from the keyDirectObject parameter. */
      err = AEGetParamDesc(&aeReply, keyDirectObject, typeChar,
      if (err == noErr)
          *output = (CStringHandle) paramDesc.dataHandle;
      /* Get the diagnostic output from the 'diag' parameter. */
      err = AEGetParamDesc (&aeReply, 'diag', typeChar,
      if (err == noErr)
          *diagnostic = (CStringHandle) paramDesc.dataHandle;
      /* Get the MPW status from the 'stat' parameter -- it */
      /* becomes our error return. */
      err = AEGetParamPtr(&aeReply, 'stat', typeInteger,
                         &theType, &theLong,
                         sizeof(long), &theSize);
      if (err == noErr) err = theLong;

   /* done with the reply descriptor */
   (void) AEDisposeDesc(&aeReply);
   return err;

The event must be created before it can be sent. For SourceServer, there's a single parameter, named keyDirectObject, which is the descriptor list containing the command. After sending the event, you must extract the results. The results of an Apple event are returned as keyword parameters in a reply descriptor. First there's the standard keyErrorNumber parameter, which returns an error code if delivery failed. SourceServer returns three other parameters: The 'stat' parameter contains a second error code; if it's nonzero, SourceServer tried to execute the command and failed. When there's an error, there will be diagnostic output in the 'diag' parameter, a handle containing text from the MPW diagnostic (error) channel. Finally, there's standard output -- a handle specified by keyDirectObject -- which contains explanatory text.


The Macintosh has always had a drag and drop user experience, but the true power and generality of dragging has been widely recognized only recently. The drag paradigm can even be used for source control. To turn Projector into a drag-savvy system, I've written a set of utilities called ProjectDrag (source code and documentation are provided on this issue's CD). You simply drag and drop icons onto the following miniapplications that make up ProjectDrag, and the corresponding function is performed:
  • Check In and Check Out, for checking files in and out

  • ModifyReadOnly, for editing a file without checking it out

  • Update, for bringing a file or folder up to date, as well as canceling checkouts and modify-read-only changes

  • ProjectDrag Setup, for configuring the system
These utilities are based on a drop-on application framework called DropShell (written by Leonard Rosenthol and Stephan Somogyi), also on the CD. When a file is dropped onto an application, the application receives an Open Documents ('odoc') event. DropShell takes care of the rigmarole of receiving this and other required Apple events. The ProjectDrag miniapplications pull the file specifications out of 'odoc' events and create SourceServer commands that operate on the files and folders that were dropped on their icons.
    DropShell is also available on the Internet at and at other Info-Mac mirror sites.*
Some setup is required. ProjectDrag needs to know the locations of Projector databases. It maps between project names and Projector database files by keeping aliases to database folders in its Preferences folder. To start using a project, simply drag its ProjectorDB file or the enclosing folder onto ProjectDrag Setup. Projector also needs to know your user name, and your initials or a nickname are used in change comments at the start of files. These are stored in a text file in the Preferences folder. ProjectDrag asks you for this information if it can't find it, or you can launch ProjectDrag Setup and give the Set User Name command.

ProjectDrag is scriptable, unlike SourceServer and the MPW Shell. The miniapplications have an Apple event terminology resource ('aete') to advertise their events to scripting systems. This allows you to add source control commands to any application that lets you add AppleScript scripts to its menus.

ProjectDrag is able to run remotely over a network. This circumvents a limitation of SourceServer, which can only be driven locally. ProjectDrag can receive remote Apple events and then drive a copy of SourceServer that's local to it. Among other uses, this could support an accelerator for Apple Remote Access. Checking a file in or out over ARA takes a few minutes, which is fine, especially for those who find tedium particularly enjoyable. Copying files is faster. With local AppleScript front ends for remote ProjectDrag miniapplications, you could copy files to and from a remote "shadow folder" and initiate SourceServer commands at the remote location, where they would execute over a fast network such as Ethernet.

I like to think that I can solve user interface problems in my sleep. When I was writing ProjectDrag, I had a dream of a better user experience. Instead of miniapplications, ProjectDrag would be a magical system extension that would put a single small icon at some convenient place on the screen. When you dragged a file onto this icon, it would pop open into a temporary window and show you icons for the various options. Dreams are great for creativity, but it's easier to weigh alternatives when you're awake. After I woke up, I realized that miniapplications will be able to do the same thing.

Here's how: In Copland, the next generation of the Mac OS, the Finder will spring-load folders so that they open automatically when you drag onto them. It will also let you stash commonly used folders at the bottom of the screen, where they appear as short title bars. Drag the ProjectDrag folder to the bottom of the screen and you're set! Since the Finder will be providing my dream interface, there's no point in a lot of trap patching and extensibility infrastructure to accomplish the same thing.

Copland will bring another user experience benefit to ProjectDrag: it's planned that document windows will have a draggable file icon in their title bar, so you'll be able to use ProjectDrag on an open document by dragging the icon from its window.


You can create programs that use SourceServer for many other tasks. On cross-platform projects, Projector is sometimes used to control both platforms' source folders. This can lead to baroque and error-prone processes. With SourceServer, you can create front ends that do the right thing. They could copy to remote folders over a network, or lock read-only files since the other platform doesn't see Projector's 'ckid' resources.

Quality is an interesting area for source control applications. A quality tool could query Projector databases for the frequency and scope of changes at various stages of the project, correlating them with bug tracking to develop project metrics. Along similar lines, a tool could measure the change rate of various files to assist in what the quality gods refer to as root-cause analysis.

SourceServer is much more than a way for development systems to provide integrated source control. It's great for structuring your internal development process as well!

TIM MARONEY wrote TOPS Terminal and BackDrop, and has been a major contributor to TOPS for Macintosh, FaxPro, and Cachet. He has also contributed to Fiery, the Disney Screen Saver, Ofoto, Colortron, and the Usenet Mac Programmer's Guide. Tim learned computer networking while working on the Andrew and MacIP projects at Carnegie Mellon and studied compiler design in graduate school at Chapel Hill. He has written for all three major operating systems and a few minor ones. On the Macintosh, Tim's code has included applications, INITs, control panels, HyperCard stacks, XCMDs, shared libraries, trap patches, plug-ins, scripts, and things more difficult to characterize. Tim is currently doing contract work at Apple, and is available for parties and special events at a nominal cost.*

Thanks to Greg Anderson, Arno Gourdol, and B. Winston Hendrickson for reviewing this column.*

Special thanks to Jens Alfke, Jon Pugh, Leonard Rosenthol, and Stephan Somogyi.*


Community Search:
MacTech Search:

Software Updates via MacUpdate

Civilization VI 1.1.0 - Next iteration o...
Sid Meier’s Civilization VI is the next entry in the popular Civilization franchise. Originally created by legendary game designer Sid Meier, Civilization is a strategy game in which you attempt to... Read more
Network Radar 2.3.3 - $17.99
Network Radar is an advanced network scanning and managing tool. Featuring an easy-to-use and streamlined design, the all-new Network Radar 2 has been engineered from the ground up as a modern Mac... Read more
Quicken 5.5.6 - Complete personal financ...
Quicken makes managing your money easier than ever. Whether paying bills, upgrading from Windows, enjoying more reliable downloads, or getting expert product help, Quicken's new and improved features... Read more
Civilization VI 1.1.0 - Next iteration o...
Sid Meier’s Civilization VI is the next entry in the popular Civilization franchise. Originally created by legendary game designer Sid Meier, Civilization is a strategy game in which you attempt to... Read more
Network Radar 2.3.3 - $17.99
Network Radar is an advanced network scanning and managing tool. Featuring an easy-to-use and streamlined design, the all-new Network Radar 2 has been engineered from the ground up as a modern Mac... Read more
Printopia 3.0.8 - Share Mac printers wit...
Run Printopia on your Mac to share its printers to any capable iPhone, iPad, or iPod Touch. Printopia will also add virtual printers, allowing you to save print-outs to your Mac and send to apps.... Read more
ForkLift 3.2.1 - Powerful file manager:...
ForkLift is a powerful file manager and ferociously fast FTP client clothed in a clean and versatile UI that offers the combination of absolute simplicity and raw power expected from a well-executed... Read more
BetterTouchTool 2.417 - Customize multi-...
BetterTouchTool adds many new, fully customizable gestures to the Magic Mouse, Multi-Touch MacBook trackpad, and Magic Trackpad. These gestures are customizable: Magic Mouse: Pinch in / out (zoom... Read more
Little Snitch 4.0.6 - Alerts you about o...
Little Snitch gives you control over your private outgoing data. Track background activity As soon as your computer connects to the Internet, applications often have permission to send any... Read more
Google Chrome 65.0.3325.181 - Modern and...
Google Chrome is a Web browser by Google, created to be a modern platform for Web pages and applications. It utilizes very fast loading of Web pages and has a V8 engine, which is a custom built... Read more

Latest Forum Discussions

See All

Construction Simulator 2 reaches its fir...
Construction Simulator 2 debuted iOS and Android devices exactly one year ago, and publisher Astragon is marking the game’s first anniversary with a range of time-limited discounts. It’s been a successful debut for the civil engineering sim, which... | Read more »
All the best games on sale for iPhone an...
This week's list of games on sale for the iPhone and iPad isn't too bad really. There's some gems on here, as well as some games that have had their prices cut low enough that you can look past the rough edges and questionable decisions. [Read... | Read more »
The best games that came out for iPhone...
It's not a huge surprise that there's not a massive influx of new, must-buy games on the App Store this week. After all, GDC is happening, so everyone's busy at parties and networking and dying from a sinister form of jetlag. That said, there are... | Read more »
Destiny meets its mobile match - Everyth...
Shadowgun Legends is the latest game in the Shadowgun series, and it's taking the franchise in some interesting new directions. Which is good news. The even better news is that it's coming out tomorrow, so if you didn't make it into the beta you... | Read more »
How PUBG, Fortnite, and the battle royal...
The history of the battle royale genre isn't a long one. While the nascent parts of the experience have existed ever since players first started killing one another online, it's really only in the past six years that the genre has coalesced into... | Read more »
Around the Empire: What have you missed...
Oh hi nice reader, and thanks for popping in to check out our weekly round-up of all the stuff that you might have missed across the Steel Media network. Yeah, that's right, it's a big ol' network. Obviously 148Apps is the best, but there are some... | Read more »
All the best games on sale for iPhone an...
It might not have been the greatest week for new releases on the App Store, but don't let that get you down, because there are some truly incredible games on sale for iPhone and iPad right now. Seriously, you could buy anything on this list and I... | Read more »
Everything You Need to Know About The Fo...
In just over a week, Epic Games has made a flurry of announcements. First, they revealed that Fortnite—their ultra-popular PUBG competitor—is coming to mobile. This was followed by brief sign-up period for interested beta testers before sending out... | Read more »
The best games that came out for iPhone...
It's not been the best week for games on the App Store. There are a few decent ones here and there, but nothing that's really going to make you throw down what you're doing and run to the nearest WiFi hotspot in order to download it. That's not to... | Read more »
Death Coming (Games)
Death Coming Device: iOS Universal Category: Games Price: $1.99, Version: (iTunes) Description: --- Background Story ---You Died. Pure and simple, but death was not the end. You have become an agent of Death: a... | Read more »

Price Scanner via

Thursday roundup of the best 13″ MacBook Pro...
B&H Photo has new 2017 13″ MacBook Pros on sale for up to $200 off MSRP. Shipping is free, and B&H charges sales tax for NY & NJ residents only. Their prices are the lowest available for... Read more
Sale: 9.7-inch 2017 WiFi iPads starting at $2...
B&H Photo has 9.7″ 2017 WiFi Apple iPads on sale for $40 off MSRP for a limited time. Shipping is free, and pay sales tax in NY & NJ only: – 32GB iPad WiFi: $289, $40 off – 128GB iPad WiFi: $... Read more
Roundup of Certified Refurbished iPads, iPad...
Apple has Certified Refurbished 9.7″ WiFi iPads available for $50-$80 off the cost of new models. An Apple one-year warranty is included with each iPad, and shipping is free: – 9″ 32GB WiFi iPad: $... Read more
Back in stock! Apple’s full line of Certified...
Save $300-$300 on the purchase of a 2017 13″ MacBook Pro today with Certified Refurbished models at Apple. Apple’s refurbished prices are the lowest available for each model from any reseller. A... Read more
Wednesday deals: Huge sale on Apple 15″ MacBo...
Adorama has new 2017 15″ MacBook Pros on sale for $250-$300 off MSRP. Shipping is free, and Adorama charges sales tax in NJ and NY only: – 15″ 2.8GHz Touch Bar MacBook Pro Space Gray (MPTR2LL/A): $... Read more
Apple offers Certified Refurbished Series 3 A...
Apple has Certified Refurbished Series 3 Apple Watch GPS models available for $50, or 13%, off the cost of new models. Apple’s standard 1-year warranty is included, and shipping is free. Numerous... Read more
12″ 1.2GHz Space Gray MacBook on sale for $11...
B&H Photo has the Space Gray 12″ 1.2GHz MacBook on sale for $100 off MSRP. Shipping is free, and B&H charges sales tax for NY & NJ residents only: – 12″ 1.2GHz Space Gray MacBook: $1199 $... Read more
Mac minis available for up to $150 off MSRP w...
Apple has restocked Certified Refurbished Mac minis starting at $419. Apple’s one-year warranty is included with each mini, and shipping is free: – 1.4GHz Mac mini: $419 $80 off MSRP – 2.6GHz Mac... Read more
Back in stock: 13-inch 2.5GHz MacBook Pro (Ce...
Apple has Certified Refurbished 13″ 2.5GHz MacBook Pros (MD101LL/A) available for $829, or $270 off original MSRP. Apple’s one-year warranty is standard, and shipping is free: – 13″ 2.5GHz MacBook... Read more
Apple restocks Certified Refurbished 2017 13″...
Apple has Certified Refurbished 2017 13″ MacBook Airs available starting at $849. An Apple one-year warranty is included with each MacBook, and shipping is free: – 13″ 1.8GHz/8GB/128GB MacBook Air (... Read more

Jobs Board

Payments Counsel - *Apple* Pay (payments, c...
# Payments Counsel - Apple Pay (payments, credit/debit) Job Number: 112941729 Santa Clara Valley, California, United States Posted: 26-Feb-2018 Weekly Hours: 40.00 Read more
Firmware Engineer - *Apple* Accessories - A...
# Firmware Engineer - Apple Accessories Job Number: 113452350 Santa Clara Valley, California, United States Posted: 28-Feb-2018 Weekly Hours: 40.00 **Job Summary** Read more
*Apple* Solutions Consultant - Apple (United...
# Apple Solutions Consultant Job Number: 113501424 Norman, Oklahoma, United States Posted: 15-Feb-2018 Weekly Hours: 40.00 **Job Summary** Are you passionate about Read more
*Apple* Inc. Is Look For *Apple* Genius Te...
Apple Inc. Is Look For Apple Genius Technical Customer Service Minneapolis Mn In Minneapolis - Apple , Inc. Apple Genius Technical Customer Service Read more
*Apple* Genius Technical Customer Service Co...
Apple Genius Technical Customer Service Columbus Oh Apple Inc. - Apple , Inc. Apple Genius Technical Customer Service Columbus Oh - Apple , Inc. Job Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.